Pon Farr is much understood. A Vulcan *must* mate every seven years at a set time, but that does not mean they do not have recreational sex of their choice when they wish in between those seven years. And it never seemed to bother Amanda, she didn’t up sticks and divorce/leave Sarek, so either it IS once every seven years and she has a low sex drive, OR humans are not the only species whom can also mate “out of season” so to speak, for recreational purposes.